Possible evidence for an energy gap below the Néel temperature in ternary rare-earth compounds

Electrical-resistivity ({ρ}) behavior in the vicinity of the N\'eel temperature (TN) of the pseudoternary alloys RCu_2-x{Ni}ₓSi₂ (R=Pr, Gd, and Dy) and R_1-x{La}ₓCu₂{Si}₂(R=Pr and Gd) is reported. There is an increase in ρ just below{T}N$ in several alloys, followed by the usual decrease at lower temperatures due to the loss of spin-disorder contribution. We attribute this rise in {ρ} to the formation of an energy gap at the Fermi surface due to antiferromagnetic ordering.